Magnetic device and method of manufacturing the same

ABSTRACT

A magnetic device comprises a lead frame, a first core body and a coil. The lead frame has a first portion and a second portion spaced apart from the first portion. A first core body is disposed on the lead frame, wherein the first core body comprises a first through opening and a second through opening. A coil is disposed on the first core body, wherein the coil has a first terminal and a second terminal, wherein the first portion is electrically connected with the first terminal via the first through opening, and the second portion is electrically connected with the second terminal via the second through opening, respectively.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/902,997, filed May 28, 2013, which claims the benefit of priority ofU.S. Provisional Application No. 61/803,798, filed Mar. 21, 2013. All ofthese applications are incorporated by referenced herein in theirentirety.

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates to a magnetic device and, in particular,to a magnetic device with electrodes made of a lead frame.

II. Description of the Prior Art

As an inductor has gradually become smaller and thinner, it is not easyto position the coil accurately which will affect product yield. Theelectrodes of the inductor are exposed to the lateral surface of theinductor so that a fixed space must be kept in the circuit board toprevent short circuit. Moreover, with the shrinkage of product size, abad C-face crack will result from a bent stress when the electrodes ofthe inductor are bent during the molding process.

So far there are some drawbacks in the various types of inductorsdisclosed in the prior arts. In JP4795489B1, the design of the inductorwhich needs many electroplating steps induces a lot of process steps;the material capable of be electroplated is limited; and the electrodesof the inductor are exposed to the lateral surface of the inductor. InCN201207320Y, the conductive wires bent to the bottom of the iron coreinduce that the iron core doesn't have a smooth surface. If pressure isstill applied in package process, the iron core easily has a crack.

Accordingly, the present invention proposes a magnetic device and amanufacturing method thereof to overcome the above-mentioneddisadvantages.

SUMMARY OF THE INVENTION

One objective of the present invention is to provide a magnetic devicewith bottom electrodes made of a lead frame. The magnetic devicecomprises: a lead frame having a first portion and a second portionspaced apart from the first portion; a first core body disposed on thelead frame, wherein the first core body comprises a first throughopening and a second through opening; and a coil disposed on the firstcore body, wherein the coil has a first terminal and a second terminal,wherein the first portion is electrically connected with the firstterminal via the first through opening, and the second portion iselectrically connected with the second terminal via the second throughopening, respectively.

Preferably, the first portion comprises a first protrusion and thesecond portion comprises a second protrusion, wherein the firstprotrusion is connected with the first terminal through the firstthrough opening, and the second protrusion is connected with the secondterminal through the second through opening, respectively. A firstconductive pillar can be disposed in the first through opening toconnect the first portion with the first terminal, and a secondconductive pillar can be disposed in the second through opening toconnect the second portion with the second terminal, respectively.

A molding body encapsulates the coil. A first electrode is disposed onthe bottom surface of the first portion and a second electrode isdisposed on the bottom surface of the second portion. That is, thebottom of each of the first portion and the second portion of the leadframe is exposed to the bottom of the molding body such that the firstportion and the second portion respectively serve as a first electrodeand a second electrode of the magnetic device. The main advantages ofthe magnetic device in the present invention are described asfollows: 1. Adhesion area between the bottom electrodes of the magneticdevice and the circuit board is maximized to enhance the adhesionstrength. 2. Because of no lateral electrode, product size can be shrunkand surface utility rate of the circuit board can be raised. 3. Theheight and the shape of the protrusions of the lead frame can beadjusted to be adapted for various types of coils so that it is easierto weld and position the core body. 4. The lead frame can be formed byvarious methods, such as folding, bending, electroplating or etching.

Another objective of the present invention is to provide a method forforming a magnetic device. The method comprises the steps of: forming alead frame having a first portion and a second portion spaced apart fromthe first portion; disposing a first core body on the lead frame,wherein the first core body comprises a first through opening and asecond through opening; and disposing a coil on the first core body,wherein the coil has a first terminal and a second terminal, wherein thefirst portion is electrically connected with the first terminal via thefirst through opening, and the second portion is electrically connectedwith the second terminal via the second through opening, respectively.In one embodiment of the magnetic device adapted for SMD technology, thelead frame can be formed by electroplating or etching.

Another objective of the present invention is to provide a method forforming a magnetic device, the method comprising the steps of: forming alead frame comprising a first bottom part and a first protrusionconnected to the first bottom part; forming a first core body, whereinthe first core body comprises a first through opening; placing the firstcore body on the first bottom part of the lead frame, with at least apart of the first protrusion of the lead frame disposed in the firstthrough opening for electrically connecting with a first terminal of acoil on the first core body; and encapsulating the first protrusion ofthe lead frame and the coil by using a molding material.

In one embodiment, the first bottom part and the first protrusion areintegrally formed.

In one embodiment, the lead frame further comprises a second bottom partand a second protrusion connected to the second bottom part, and whereinthe first core body further comprises a second through opening, whereinthe first core body is placed on the first bottom part of the lead frameand at least a part of the second protrusion of the lead frame isdisposed in the second through opening for electrically connecting witha second terminal of the coil on the first core body.

In one embodiment, the first bottom part and the first protrusion areintegrally formed, and the second bottom part and the second protrusionare integrally formed.

In one embodiment, the lead frame is formed by electroplating aconductive pillar on a conductive material.

In one embodiment, the lead frame is formed by electroplating aconductive pillar on a copper foil.

In one embodiment, the lead frame is formed by etching a metallicsubstrate.

In one embodiment, the first protrusion comprises a first foldablesoldering pad.

In one embodiment, the first protrusion comprises a first bent portionfor connecting with the first terminal.

In one embodiment, the first through opening is formed with a firstouter side surface of the first core body.

In one embodiment, the first through opening is formed with two outerside surfaces of the first core body.

In one embodiment, the first through opening is formed with a firstouter side surface of the first core body; and the second throughopening is formed with a second outer side surface of the first corebody.

In one embodiment, the first through opening and the second throughopening are respectively formed with two outer side surfaces of thefirst core body.

In one embodiment, the first through opening and the second throughopening are respectively formed on a periphery of the first core body,wherein the first protrusion is not extended outside of any outer sidesurface of the first core body adjacent to the first through opening,and the second protrusion is not extended outside of any outer sidesurface of the first core body adjacent to the second through opening.

The detailed technology and above preferred embodiments implemented forthe present invention are described in the following paragraphsaccompanying the appended drawings for people skilled in this field towell appreciate the features of the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the accompanying advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed descriptionwhen taken in conjunction with the accompanying drawings, wherein:

FIG. 1A is a schematic view of a magnetic device in the presentinvention;

FIG. 1B is an exploded schematic view of the magnetic device shown inFIG. 1A;

FIG. 1C is a bottom schematic view of the magnetic device shown in FIG.1A;

FIG. 1D is an exploded schematic view of the magnetic device, whereinthe first core body is a T-core body;

FIG. 1E is a schematic view of the magnetic device in the presentinvention, wherein the first core body is a T-core body;

FIG. 2A is a schematic view of a foldable lead frame, wherein thefoldable lead frame is unfolded;

FIG. 2B is a schematic view of a foldable lead frame;

FIG. 2C is a schematic view of a magnetic device in the presentinvention, wherein the lead frame is foldable;

FIG. 2D is a schematic view of a bent lead frame;

FIG. 3 is the process flow of manufacturing a magnetic device in FIG.1A, FIG. 1E, FIG. 2C and FIG. 4A;

FIG. 4A is a schematic view of a magnetic device in the presentinvention, wherein the lead frame is formed by electroplating oretching;

FIG. 4B is an exploded schematic view of the magnetic device shown inFIG. 4A.

DETAILED DESCRIPTION OF THE INVENTION

The detailed explanation of the present invention is described asfollowing. The described preferred embodiments are presented forpurposes of illustrations and description and they are not intended tolimit the scope of the present invention.

The present invention discloses a magnetic device in which a firstportion and a second portion of a lead frame respectively areelectrically connected with a first terminal and a second terminal of acoil through a first through opening and a second through opening of acore body to serve as a first electrode and a second electrode on thebottom of the magnetic device.

FIG. 1A is a schematic view of a magnetic device 10 in the presentinvention. FIG. 1B is an exploded schematic view of the magnetic device10 shown in FIG. 1A. FIG. 1C is a bottom schematic view of the magneticdevice 10 shown in FIG. 1A. FIG. 1D is an exploded schematic view of themagnetic device 10, wherein the first core body is a T-core body. FIG.1E is a schematic view of the magnetic device 10 in the presentinvention, wherein the first core body is a T-core body. The magneticdevice 10 includes a lead frame 11, a first core body 12, a coil 13 anda molding body 14.

The lead frame 11 has a first portion 11 a and a second portion 11 bspaced apart from the first portion 11 a. Optionally, the first portion11 a can comprise a first protrusion 15 a, and the second portion 11 bcan comprise a second protrusion 15 b. For a better electricalconnection between the lead frame 11 and the coil 13, the top of thefirst protrusion 15 a is higher than that of the first through opening12 a, and the top of the second protrusion 15 b is higher than that ofthe second through opening 12 b. Preferably, the first portion 11 afurther comprises a third protrusion 15 c, and the second portion 11 bfurther comprises a fourth protrusion 15 d, wherein the first protrusion15 a, the second protrusion 15 b, the third protrusion 15 c and thefourth protrusion 15 d surround the first core body 12. In oneembodiment (see FIG. 2A, FIG. 2B and FIG. 2C), the first protrusion 15 acomprises a first foldable soldering pad 17 a, and the second protrusion15 b comprises a second foldable soldering pad 17 b. Specificallyspeaking, the first portion 11 a of the lead frame 11 has a firstfoldable soldering pad 17 a folded to serve as the first protrusion 15a, and the second portion 11 b of the lead frame 11 has a secondfoldable soldering pad 17 b folded to serve as the second protrusion 15b. In another embodiment (see FIG. 2D), the first protrusion 15 acomprises a first bent portion for connecting with a first terminal of acoil, and the second protrusion 15 b comprises a second bent portion forconnecting with the second terminal of a coil. For example, the firstprotrusion 15 a, the second protrusion 15 b, the third protrusion 15 c,the fourth protrusion 15 d can be formed by bending four segments of aflat lead frame 11. Moreover, the lead frame 11 can be also formed byelectroplating or etching (described hereafter).

A first core body 12 is disposed on the lead frame 11. The first corebody 12 is a magnetic core body. The first core body 12 can be made ofany suitable magnetic powder, such as Fe alloy powder (Fe—Cr—Si,Fe—Al—Cr or Fe—Si—Al), ferrite powder (Ni—Zn ferrite or Mn—Zn ferrite),amorphous alloy powder or Fe powder. By pressing-molding process (e.g.,heating or sintering), the magnetic powder and adhesive are mixed toform the first core body 12. The first core body 12 can have anysuitable shape according design or practical application.

The first core body 12 comprises a first through opening 12 a and asecond through opening 12 b. There are many different ways to locate thefirst through opening 12 a and the second through opening 12 b: in oneembodiment, each of the first through opening 12 a and the secondthrough opening 12 b is formed inside the first core body 12; in anotherembodiment, each of the first through opening 12 a and the secondthrough opening 12 b is formed with one side of the opening aligned withone edge of the first core body 12; and in yet another embodiment, eachof the first through opening 12 a and the second through opening 12 b isformed with two sides of the opening aligned with two edges of the firstcore body 12 respectively.

A coil 13 is disposed on the first core body 12. The coil 13 can beformed by wrapping round-wire, flat-wire or enameled-wire made of Cu orAg. The coil 13 can be made of a conductive wire or a conductive patternformed by any known technology, such as electroplating, etching,printing process or film process. The coil 13 has a first terminal 13 aand a second terminal 13 b. The first portion 11 a is electricallyconnected with the first terminal 13 a via the first through opening 12a, and the second portion 15 b is electrically connected with the secondterminal 13 b via the second through opening 12 b, respectively.Preferably, the first portion 11 a comprises a first protrusion 15 a andthe second portion 11 b comprises a second protrusion 15 b, wherein thefirst protrusion 15 a is connected with the first terminal 13 a throughthe first through opening 12 a, and the second protrusion 15 b isconnected with the second terminal 13 b through the second throughopening 12 b, respectively. In one embodiment, the top end of the firstprotrusion 15 a can be disposed in the first through opening 12 a, andthe top end of the second protrusion 15 b can be disposed in the secondthrough opening 12 b. In other words, refer to FIG. 1E and FIG. 4A, thefirst joined point 16 a of the first terminal 13 a and the firstprotrusion 15 a can be inside the first through opening 12 a, and thesecond joined point 16 b of the second terminal 13 b and the secondprotrusion 15 b can be inside the second through opening 12 b. Inanother embodiment, at least one portion of the first protrusion 15 a isdisposed outside the first through opening 12 a, and at least oneportion of the second protrusion 15 b is disposed outside the secondthrough opening 12 b. In other words, refer to FIG. 1A, the first joinedpoint 16 a of the first terminal 13 a and the first protrusion 15 a issubstantially higher than the top of the first through opening 12 a, andthe second joined point 16 b of the second terminal 13 b and the secondprotrusion 15 b is substantially higher than the top of the secondthrough opening 12 b.

A first conductive pillar (not shown) can be disposed in the firstthrough opening 12 a to connect the first portion 11 a with the firstterminal 13 a, and a second conductive pillar (not shown) can bedisposed in the second through opening 12 b to connect the secondportion 11 b with the second terminal 13 b, respectively. It has beendisclosed in U.S. patent application Ser. No. 13/179,884, filed Jul. 11,2011.

There are many different ways to dispose the coil 13 on the first corebody 12. In one embodiment (see FIG. 1A and FIG. 1B), the first core boy12 has a first surface 12 c which is substantially flat, wherein thecoil 13 is disposed on the first surface 12 c of the first core body 12.In another embodiment (see FIG. 1E, FIG. 2C and FIG. 4A), the first coreboy 12 (e.g., T-core) comprises a plate 12 e and a pillar 12 f having atop end and a bottom end, wherein the bottom end of the pillar 12 f isconnected to the plate 12 e, wherein the coil 13 is disposed on theplate 12 e and winded around the pillar 12 f. In one embodiment, themagnetic device 10 further comprises a second core body (not shown),wherein the coil 13 is disposed between the first core body 12 and thesecond core body. The material of the first core body 12 can be the sameas that of the second core body or different from that of the secondcore body.

The second core body is a magnetic core body. The second core body canbe made of any suitable magnetic powder, such as Fe alloy powder(Fe—Cr—Si, Fe—Al—Cr or Fe—Si—Al), ferrite powder (Ni—Zn ferrite or Mn—Znferrite), amorphous alloy powder or Fe powder. By pressing-moldingprocess (e.g., heating or sintering), the magnetic powder and adhesiveare mixed to form the second core body. The second core body can haveany suitable shape according design or practical application.

A molding body 14 encapsulates the coil 13. A first electrode isdisposed on the bottom surface of the first portion 11 a and a secondelectrode is disposed on the bottom surface of the second portion 11 b.That is, the bottom of each of the first portion 11 a and the secondportion 11 b of the lead frame 11 is exposed to the bottom of themolding body 14 such that the first portion 11 a and the second portionrespectively 11 b serve as a first electrode and a second electrode ofthe magnetic device 10. The first electrode and the second electrode ofthe magnetic device 10 can be formed by printing or electroplating.

FIG. 3 is the process flow of manufacturing a magnetic device 10, 20, 30in FIG. 1A, FIG. 1E, FIG. 2C and FIG. 4A.

In step 31, form a lead frame 11 having a first portion 11 a and asecond portion 11 b spaced apart from the first portion 11 a.Optionally, the first portion 11 a can comprise a first protrusion 15 aand the second portion 11 b can comprise a second protrusion 15 b.

In one embodiment of the magnetic device adapted for SMD technology, thelead frame can be formed by electroplating or etching. FIG. 4A is aschematic view of a magnetic device 30 in the present invention, whereinthe lead frame 11 is formed by electroplating or etching. FIG. 4B is anexploded schematic view of the magnetic device 30 shown in FIG. 4A. Toform the lead frame 11, for example, Sn or Ni/Sn can be electroplated ona conductive material (e.g., copper foil) which can be made of Cu, or aconductive material (e.g., a metallic substrate) can be etched. In thiscase, each of the first protrusion 15 a and the second protrusion 15 bis a conductive pillar. The advantages are listed as below: 1. Themagnetic device has a complete electrode plane, and the plane shape canbe adjusted according to design demand. Compared to the lead frameformed by bending, the bottom electrodes of the magnetic device arecomplete, and adhesion area between the bottom electrodes of themagnetic device and the circuit board is maximized (utility rate ofelectrode area is larger than 90%) to enhance the adhesion strength. 2.The height and the shape of the protrusive conductive pillars can beadjusted to be adapted for various types of coils so that it is easierto weld and position the core body. 3. The design of the bottomelectrodes of the magnetic device can reduce the distance betweendevices on the circuit board. 4. The lead frame can be directly adaptedfor SMD technology, so the electroplating steps in the process of themagnetic device can be saved and the material capable of beelectroplated is not limited.

In step 32, dispose a first core body 12 on the lead frame 11, whereinthe first core body 12 comprises a first through opening 12 a and asecond through opening 12 b. In one embodiment, the magnetic devicefurther comprises a second core body (not shown), wherein the coil isdisposed between the first core body 12 and the second core body. Thefirst core body 12 (or the second core body) is a magnetic core body.The material of the first core body 12 can be the same as that of thesecond core body or different from that of the second core body. Thefirst core body 12 (or the second core body) can be formed byhot-pressing molding or cold-pressing molding, preferably, cold-pressingmolding.

In step 33, dispose a coil 13 on the first core body 12, wherein thecoil 13 has a first terminal 13 a and a second terminal 13 b, whereinthe first portion 11 a is electrically connected with the first terminal13 a via the first through opening 12 a, and the second portion 11 b iselectrically connected with the second terminal 13 b via the secondthrough opening 12 b, respectively. Preferably, the first portion 11 acomprises a first protrusion 15 a and the second portion 11 b comprisesa second protrusion 15 b, wherein the first protrusion 15 a is connectedwith the first terminal 13 a through the first through opening 12 a, andthe second protrusion 15 b is connected with the second terminal 13 bthrough the second through opening 12 b, respectively. A firstconductive pillar (not shown) can be disposed in the first throughopening 12 a to connect the first portion 11 a with the first terminal13 a, and a second conductive pillar (not shown) can be disposed in thesecond through opening 12 b to connect the second portion 11 b with thesecond terminal 13 b, respectively. The coil 13 can be formed bywrapping round-wire, flat-wire or enameled-wire made of Cu or Ag. Thecoil 13 can be made of a conductive wire or a conductive pattern formedby any known technology, such as electroplating, etching, printingprocess or film process.

In step 34, form a molding body 14 to encapsulate the coil 13. Themolding body 14 can be formed by hot-pressing molding or cold-pressingmolding, preferably, hot-pressing molding. A first electrode is disposedon the bottom surface of the first portion 11 a and a second electrodeis disposed on the bottom surface of the second portion 11 b. That is,the bottom of each of the first portion 11 a and the second portion 11 bof the lead frame 11 is exposed to the bottom of the molding body 14such that the first portion 11 a and the second portion 11 brespectively serve as a first electrode and a second electrode of themagnetic device. The first electrode and the second electrode of themagnetic device can be formed by printing or electroplating.

Detailed process is listed as below. A lead frame is formed by punching,electroplating or etching, and then the lead frame is dispensed. A corebody is formed by cold-pressing molding and connected to the lead frame.The coil is disposed on the core body, and the terminals of the coil areelectrically connected to the protrusions of the lead frame by spotwelding or laser welding plus wire-head trimming. A molding body isformed to encapsulate the coil by hot-pressing molding and curing. Theelectrodes of the magnetic device are formed by electroplating orprinting. Finally, the final product is done by trimming and passingelectrical testing.

The above disclosure is related to the detailed technical contents andinventive features thereof. People skilled in this field may proceedwith a variety of modifications and replacements based on thedisclosures and suggestions of the invention as described withoutdeparting from the characteristics thereof. Nevertheless, although suchmodifications and replacements are not fully disclosed in the abovedescriptions, they have substantially been covered in the followingclaims as appended.

What is claimed is:
 1. A method for forming a magnetic device, themethod comprising the steps of: forming a lead frame comprising a firstbottom part and a first protrusion connected to the first bottom part;forming a first core body, wherein the first core body comprises a firstthrough opening; placing the first core body on the first bottom part ofthe lead frame, with at least a part of the first protrusion of the leadframe disposed in the first through opening for electrically connectingwith a first terminal of a coil on the first core body; andencapsulating the first protrusion of the lead frame and the coil byusing a molding material.
 2. The method according to claim 1, whereinthe first bottom part and the first protrusion are integrally formed. 3.The method according to claim 1, wherein the lead frame furthercomprises a second bottom part and a second protrusion connected to thesecond bottom part, and wherein the first core body further comprises asecond through opening, wherein the first core body is placed on thefirst bottom part of the lead frame and at least a part of the secondprotrusion of the lead frame is disposed in the second through openingfor electrically connecting with a second terminal of the coil on thefirst core body.
 4. The method according to claim 3, wherein the firstbottom part and the first protrusion are integrally formed, and thesecond bottom part and the second protrusion are integrally formed. 5.The method according to claim 1, wherein the lead frame is formed byelectroplating a conductive pillar on a conductive material.
 6. Themethod according to claim 1, wherein the lead frame is formed byelectroplating a conductive pillar on a copper foil.
 7. The methodaccording to claim 1, wherein the lead frame is formed by etching ametallic substrate.
 8. The method according to claim 2, wherein thefirst protrusion comprises a first foldable soldering pad.
 9. The methodaccording to claim 2, wherein the first protrusion comprises a firstbent portion for connecting with the first terminal.
 10. The methodaccording to claim 1, wherein the first through opening is formed with afirst outer side surface of the first core body.
 11. The methodaccording to claim 1, wherein the first through opening is formed withtwo outer side surfaces of the first core body.
 12. The method accordingto claim 1, further comprising a second core body, wherein the coil isdisposed between the first core body and the second core body.
 13. Themethod according to claim 1, wherein the first core boy has a firstsurface which is substantially flat, wherein the coil is disposed on thefirst surface of the first core body.
 14. The method according to claim3, wherein the first core boy comprises a plate and a pillar having atop end and a bottom end, wherein the bottom end of the pillar isconnected to the plate, wherein the coil is disposed on the plate andwound around the pillar, wherein the molding material encapsulates thecoil, the first protrusion, the second protrusion and a top portion ofthe pillar.
 15. The method according to claim 3, wherein a firstelectrode is formed on the first bottom part of the lead frame, and asecond electrode is formed on the second bottom part of the lead frame.16. The method according to claim 3, wherein the top end of the firstprotrusion is disposed in the first through opening, and the top end ofthe second protrusion is disposed in the second through opening.
 17. Themethod according to claim 3, wherein at least one portion of the firstprotrusion is disposed outside the first through opening, and at leastone portion of the second protrusion is disposed outside the secondthrough opening.
 18. The method according to claim 3, wherein the firstthrough opening is formed with a first outer side surface of the firstcore body; and the second through opening is formed with a second outerside surface of the first core body.
 19. The method according to claim3, wherein the first through opening and the second through opening arerespectively formed with two outer side surfaces of the first core body.20. The method according to claim 3, wherein the first through openingand the second through opening are respectively formed on a periphery ofthe first core body, wherein the first protrusion is not extendedoutside of any outer side surface of the first core body adjacent to thefirst through opening, and the second protrusion is not extended outsideof any outer side surface of the first core body adjacent to the secondthrough opening.